The long-term goals of this research are to identify and characterize the deoxyribonucleases (DNases) in human blood serum with respect to to distinguishing enzymatic and physical characteristics, tissue(s) of orgin, and qualitative and quantitative variations in activity that have diagnostic value for malignant diseases. Present evidence suggests that the most likely origin for serum DNase I type activity is the blood leucocytes. These hypotheses will receive special emphasis in this research. Fluorescence assays have been developed for the quantitation and electrophoretic characterization of DNases. These assays measure endonucleolytic breakage of PM2 DNA and are sensitive to as little as 1 picogram of DNase. Studies will be performed on DNase activities purified from human blood serum and pancreas. Quantitative and qualitative changes in the DNase activities in serum from patients with cancer of the pancreas or the hematopoetic system will be evaluated in terms of their diagnostic value.